1. Field of the Invention
This invention generally relates to reworking of asphalt road surfaces and more particularly to a method and apparatus for renewing the surface of asphaltic paving at low cost for immediate reuse.
2. Description of the Prior Art
The use of asphalt for paving of highways, parking areas and the like is widespread since this material provides an effective and relatively low cost surface. However, such surfaces have a limited lifetime due to problems from heat generated by traffic and weathering. For example, the top surface of an asphalt pavement may become highly oxidized or polmerized due to these heat sources. When this occurs, the normal resiliency of the asphalt is materially affected, followed by cracking and breaking of the surface. This action produces holes and irregularities in the paved surface and eventually leads to a requirement for repaving or reworking of the surface. It is known to break up damaged asphalt paving surfaces, transport the material to a plant for reprocessing and adding of new asphalt, and thereafter relaying the surface. While somewhat lower cost than repaving with all new material, the cost of such method is relatively high and time consuming, requiring removal of the roadway from service.
In the prior art, a number of methods have been proposed and utilized to renew asphaltic paving surfaces without the necessity of completely rebuilding or replacing the surface. These known processes generally include the addition of new asphalt or other similar materials, rejuvenating compounds, and the like. Also such processes involve picking up of the broken asphalt into a chamber or device for rejuvenation and replacing the material on a reworked road bed.
It is also known to rework the asphalt in situ, however, all known in situ processes involve the use of new material such as rejuvenating liquids, fresh asphalt, lime rock, and numerous other materials.
For example, Neville in U.S. Pat. No. 3,055,280 teaches a means for treating an asphalt pavement by use of a liquid reconditioning agent disclosing a "rake" device to work the surface to obtain penetration of the reconditioning agent. The crux of the Neiille patent is the use of highly penetrative radiant energy to make the asphalt highly receptive to the liquid reconditioning agent.
U.S. Pat. No. 4,261,669 to Edo teaches a steam heating means for rejuvenation, the method disclosed involves scooping up cut-up asphalt, heating in a heat chamber, and thereafter discharging the salvaged material in the form of sludge.
A patent to Jackson, Sr., U.S. Pat. No. 3,997,276, uses burner units which have the deleterious effect of further oxidizing the surface asphalt. Jackson contemplates machine for evening out distortions and irregularities; planing off oxidized and brittle portions before resurfacing; scarifying the surface preparatory to resurfacing; applying a rejuvenating agent and new resurfacing material; and compaction.
Rank et al, U.S. Pat. No. 3,732,023, disclose apparatus which processes old asphalt by mixing with lime, cement, or emulsified asphalt to produce a new base for a new road surface.
U.S. Pat. No. 1,952,452 to Monroe discloses means for planing and grading asphalt-type road surfaces after heating and scarifying. A major difficulty with the Monroe approach is that only the surface of the roadway is broken up or scarified and the heated material is simply scraped for leveling. Therefore, such an approach does little more than smooth out surface irregularities and does nothing to actually renew the surface.
In U.S. Pat. No. 3,989,401 to Moench, apparatus is described which scarifies the heated surface of the roadway which is then leveled by a screed device. In this patent, temperatures of 2400.degree. F. are required for operation of the apparatus. Unfortunately, these high temperatures tend to further degrade the asphaltic material. Other patents, such as U.S. Pat. No. 4,124,325 and No. 4,172,679, teach the renewing of asphaltic roadway surfaces by breaking up the old surface and generally mixing new materials with the older materials and redistributing the supplemented material over the roadway. Thus, this approach has the disadvantage of additional cost of fresh material plus the requirement for mixing the new materials and the materials to be reused.